Predicting Injectivity Decline in Water Injection Wells by Upscaling On-site Core Flood Data

Abstract

Predicting Injectivity Decline in Water Injection Wells by Upscaling On-site Core Flood Data

Particles suspended in water used for injection into hydrocarbon reservoirs for secondary oil recovery can result in blockage of the reservoir rock pore throats, resulting in injectivity decline of injection wells. particle such as biomass, corrosion products, silt and scale can be present, even in the most highly treated water injection systems. On-site core flooding is a well accepted method to directly measure the plugging effects of ‘live’ system water quality specification to minimise formation damage.

A major on-site core flooding study was undertaken on a large and complex seawater injection system in Saudi Arabia. Water from the Arabian Gulf is treated by filtration and deaeration before distribution through a long complex, network of flowlines, some of which are bare carbon steel and some fusion bonded epoxy lined. This results in different particle types in different areas of the system, particularly with respect to bacteria and iron. Further, the water is injected into different areas of the field, with permeabilities ranging from <10 mD to >1000 mD.

Data from the on-site coreflooding were combined with subsequent laboratory analysis of the particles and core plugs to determine the effects of the different water qualities on permeability. These data were then processed, upscaled to model injection wells and, finally history matched to long term injectivity records. This enabled a matrix of water quality specifications to be derived for each area of the field, to give projected improvements in injection well half-lives ranging from 50% to 100%.